The present invention relates to stone rollers, particularly for paper making or cardboard manufacturing machines. The roller body of a stone roller is typically comprised of natural stone such as granite, although artificial stone, such as concrete polymer, can also be used.
An example of a stone roller is disclosed in U.S. Pat. No. 4,272,873. As shown in FIG. 1 of that patent, an axial borehole of relatively large cross-section is formed in the roller body. Several tie-rods extend through the borehole and serve to connect together a pair of disk-shaped end clamping plates. The tie-rods are held by nuts which clamp the clamping plates against the ends of the roller body. Journals which rest in bearings are screwed onto the clamping plates, which enable the roller to rotate easily and provide end support for the roller. In another embodiment, shown in FIG. 2 of U.S. Pat. No. 4,272,873, the clamping plates and journals are formed together as a single piece. Either of these clamping plate/journal configurations can be used with the present invention.
In the embodiment shown in FIG. 1 of U.S. Pat. No. 4,272,873, the tie-rods are all placed relatively close radially to the inner wall of the borehole, so that the center of the stone roller is comprised merely of filler material, e.g. concrete. This construction contrasts with prior stone rollers in which a single, thick tie-rod was extended through the center of the stone roll. The present invention can only be used in conjunction with a stone roller of the type shown in FIG. 1 of U.S. Pat. No. 4,272,873, i.e. with a central borehole in the roller body. The other embodiment, shown in FIG. 2 of U.S. Pat. No. 4,272,873, in which a separate borehole is provided for each tie-rod near the outer wall of the roller body has many of the advantages of the present invention (described below), but it is quite difficult to manufacture such boreholes.
In the stone roller shown in FIG. 1 of U.S. Pat. No. 4,272,873, the tie-rods are embedded in the hardened concrete filler material. Since the tie-rods are thus rigidly bonded over their entire length to the roller body, they are prevented from vibrating or flexing under centrifugal force, and are shielded from corrosive elements.
One disadvantage of the stone roller embodiment shown in FIG. 1 of U.S. Pat. No. 4,272,873 is that a very large amount of filler material is required since the entire interior of the roller body must be filled. This makes the finished stone roller unnecessarily heavy and quite expensive to manufacture. Furthermore, the ends of the tie-rods which pass through the clamping plates are not sufficiently, if at all, covered by the filler material, and thus additional measures are required to protect them from corrosion.
Others have attempted to eliminate tie-rod oscillation by rigidly clamping the tie-rods in several stages along the axial length of the roller. This construction, however, is unsatisfactory because of the difficulty involved in assembly.